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Re: httpbis-p6-cache-06 and no-store response directive

From: Jamie Lokier <jamie@shareable.org>
Date: Mon, 8 Jun 2009 04:07:39 +0100
To: Mark Nottingham <mnot@mnot.net>
Cc: "Yngve N. Pettersen" <yngve@opera.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-ID: <20090608030739.GR15426@shareable.org>
Mark Nottingham wrote:
> Hi Yngve,
> 
> I think the your question should be posed as: what compromises the  
> cache subsystem?
> 
> In a browser, the HTML parser component would dispatch requests to a  
> cache, which then either satisfies the requests or forwards them. If  
> an HTML page has three references to <http://example.com/foo.gif>, for  
> example, there are two ways of approaching this problem;
> 
> 1) asking the cache for foo.gif once (perhaps by piggybacking the  
> callbacks for subsequent images into the first instance), or

I think it might be worth describing under what circumstances a
browser is allowed (and maybe encouraged) to do this with no-store
responses, as well as no-cache and uncachable responses generally.

In other words, when can a browser reasonably use the same response in
multiple ways, and when must it issue new requests?  We can't dictate
browser behaviour, of course, but we might be able to devise a useful
guideline.

There is little point in a web page with multiple references a
no-store/no-cache image from triggering multiple requests to that
image, and doing so makes no-store/no-cache less unusable if there are
hundreds of such references and a browser works that way.

I think I recall some version of IE where a web page containing a
"rollover" changing image would issue a new request every time the
image changed, if it was served with no-cache, making no-cache less
useful.

-- Jamie
Received on Monday, 8 June 2009 03:08:16 GMT

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